1. Field of the Invention
This invention relates to a novel composition for use in dental flosses or tapes. More particularly, it relates to novel compositions containing a base polymer, a block copolymer and a nonmigrating compatibilizer or plasticizer that, in combination in a blend, result in a floss or dental tape having good breaking strength, tenacity, nick resistance and elongation properties. It also relates to a novel extruded, flattened, monofilament tube structure useful in dental tapes and flosses, as well as a method for making such structure. It also relates to a flattened monofilament tube that is textured along the longitudinal axis as well as perpendicular to this axis.
2. Prior Art
The use of polymer compositions in dental flosses and tapes has been known previously. However, there have been continuous efforts to develop a floss which does not shred or fray upon use and which has sufficient tensile strength for use between the teeth.
For example, U.S. Pat. No. 2,381,142 (Stonehill) describes a dental floss made from a strand or filament of synthetic fibers of an unplasticized vinyl resin such as a copolymer of vinyl chloride and vinyl acetate treated with wax.
U.S. Pat. No. 3,359,344 (Fukushima) describes a method for manufacturing a spun fiber. According to Fukushima, a polymer selected from the group of polyethylene, polypropylene and polystyrene having a melting point lower than 170.degree. C. is mixed with a second polymer selected from polyamides and polyesters having a melting point greater than 170.degree. C. and an additional amount of the first polymer. The composition is blended and extruded to form a fiber.
In U.S. Pat. No. 3,639,505 (Hughes et al.), there is described a method of improving the dyeability of polyolefin fibers and films. The method includes forming a polymer alloy containing a blend of polyolefin, a minor amount of polyethylene terephthalate and from 0.2 to 5 parts per hundred parts of polymer of toluenesulfonamide compound.
U.S. Pat. No. 3,800,812 (Jaffe) describes a dental floss made from a polyester elastomer, including Hytrel (available from DuPont). The elastomer is extruded into a hot and tacky tape, then cooled.
U.S. Pat. No. 3,900,549 (Yamane et al.) describes a method for preparing composite filaments composed of a polyethylene and a polyester. The method includes the steps of mixing a polyethylene having a melt index of above 27 with a polyester having a specific inherent viscosity, the proportion of the polyethylene being 5 to 15% or 25 to 90% based on the total weight of the mixture, melt extruding the resulting mixture through a spinneret and then withdrawing the extruded filaments at a speed of above 2,500 meters per minute.
U.S. Pat. No. 3,957,056 (Ferraro et al.) describes a dental floss containing aromatic polyamide fibers having at least 35% of the amide linkages attached directly to two aromatic rings.
U.S. Pat. No. 4,552,603 (Harris, Jr. et al) describes heat bondable bicomponent fibers containing polyester and another thermoplastic polymer having a melting point which is at least 15% C. below that of polyester.
U.S. Pat. No. 4,583,564 (Finkelstein et al.) describes a dental floss consisting of filaments containing a higher melting point core material and a lower melting point sheath material. The sheath material fibers are fused by subjecting them to a temperature sufficient to fuse them.
U.S. Pat. No. 4,609,710 (Iohara et al.) describes an undrawn polyester yarn and process for manufacturing such yarn. The main acid component of the yarn is an aromatic dicarboxylic acid.
U.S. Pat. No. 4,986,288 (Kent et al.) describes dental floss and toothpicks which contain one or more coagulants to retard and stop bleeding during flossing.
U.S. Pat. No. 4,996,056 (Blass) describes a dental floss or tape containing fluorocarbon polymer powder particles as a solid lubricant.
Despite the existence of such products as described heretofore, there still exists a need for dental floss and tape products having high breaking strength, high tenacity, nick resistance and suppleness which does not fray or break easily when used. Furthermore, there is a need to have dental floss or tape which is gentle to gum tissue which can be manufactured at high speed and low cost.
It is, therefore, an object of this invention to provide an extruded, flattened, monofilament tube with rounded edges suitable for use as a dental floss or tape.
It is another object of this invention to provide a flattened, monofilament tube that is textured along the longitudinal axis as well as perpendicular to this axis.
It is another object of this invention to provide a polymer blend resulting in an acceptable dental floss or tape.
It is another object of this invention to provide a dental floss or tape having high breaking strength, high tenacity, nick resistance and suppleness which does not fray or break in use.
Another object of this invention is to provide a method for making a polymer blend resulting in an excellent composition for use in dental flosses and tapes.
Another object of this invention is to provide a method of making polymer blend products in the form of a monofilament for use as a dental tape or floss.
Yet another object of this invention is to provide low cost, high grade polymer compositions for use in dental flosses and tapes.
Additional objects will become apparent throughout the ensuing description of the products and processes of this invention.